Isolated microtubule proteins from calf brain will undergo ATP-dependent gelation and contraction. Microtubules in these gels form bundles and structures resembling mitotic asters and spindles. Directed particle movements are observed in contracting gels. The proposed experiments will explore the chemistry and physiology of microtubule gelation-contraction. The proteins necessary for gelation-contraction will be isolated and their physical, chemical and enzymatic properties characterized by standard techniques. Optimum conditions for gelation-contraction will be determined and the role of ATP in microtubule gelation, aster formation and gel contraction will be examined. The nature and role of the motile particulates that form microtubule focal centers will be investigated. The structure of gels and the polarity of microtubules will be explored by electron microscopy. The relationship of microtubule gelation-contraction to nerve cell development will be examined by isolating microtubule proteins from animals at different ages. Actin and neurofilament proteins will be added to microtubule gels to study cytoskeletal interactions in vitro. Motile phenomenon in microtubule gels will be investigated by video enhanced contrast microscopy. The relationship of microtubule gelation-contraction to mitosis will be explored by isolating microtubule proteins from dividing surf clam eggs. Antibodies against gelation-contraction proteins will be prepared and used to localize these proteins in dividing cells and developing neurons. These experiments will help establish the role of microtubules in the morphology and motility of living cells.